# How do I fix an Omron d2fc-f-7n microswitch from unwanted clicks?

Omron d2fc-f-7n microswitches are used in computer mice all around, and they eventually start clicking several times per hit. AFAIK there is a flexible metal plate that wears out due to metal fatigue, so there must be a way to prolong its life.

The obvious solution is to remove the malfunctioning microswitch and replace with a spare, but where I live they aren't available at all.

• Nowadays you can buy electronic components from online stores which deliver them all over the world (e.g. farnell.com | digikey.com | futureelectronics.com ) – m.Alin Apr 15 '12 at 11:09
• Delivery costs many times more than the items themselves, so I'd rather repair it. – user1306322 Apr 15 '12 at 11:26
• i got a 3 years old razer mamba with heavily playing dota 2, recently it got worse, left button always double clicking, right button too. I opened up the switch, bend the piece of metal, put them all back in place and TADAA, both of my Mamba buttons are fixed, the click sound is as loud as the new one, (maybe louder, more solid), I have flatten the metal a little too much, well it's fine, my mouse is fixed without replacing a new switch. – user37375 Feb 18 '14 at 13:35
• It must be a really expensive mouse, I can buy a brand new Logitech one for about \$5, doesn't seem worth the time repairing the old one. – John U Feb 18 '14 at 19:25
• @JohnU yup, it's a razer mouse. Quite expensive. – user1306322 Feb 19 '14 at 3:37

Delivery costs many times more than the items themselves

Even from eBay? Whereabouts do you live?

One way you can get spares is to smash open another mouse that's broken for some other reason. Perhaps a friend has a broken one?

It may be possible to repair them. Those little switches have a snap fit cover, and can be opened up.

carefully pull on the catch with a fine blade, and remove the cover.

At this point, plug in the mouse and test the switch. gently push on the metal spring on the switch, and see if the problem still happens. If not, try to push on it in such a way that the problem happens. After you have attempted to fix the switch, you will be able to test it again without re-assembling the whole mouse.

Unplug the mouse now.

The switches come in a variety of different designs, but they are fairly similar. There's a bistable metal spring which normally serves to ensure the contacts move rapidly and decisively. Either it's this spring which isn't pulling as hard, or the contacts are dirty.

You need to flatten it slightly. You might find it easier to remove the spring from the switch first. Place it on a table, and squash it slightly with your finger. Not too much. Better to err on the side of caution.

Then put the spring back in the switch. Test it again now. If it still bounces, then you might need to flatten the spring a little more. If this doesn't work, then try cleaning the contacts.

Tear off a thin (5mm wide) strip of J-Cloth or similar.

Apply a little abrasive cleaner (like CIF) to it. Thread it through the switch and pull it back and forth to rub away any dirt from the contacts.

Tear off another strip, and soak it in methylated spirits (or pure alcohol). Use this to clean off the abrasive cleaner.

Test the switch again. If it still doesn't work, then get a new switch.

• Those look like SPDT switches, which can be trivially debounced with a couple of NAND gates (SR latch). Is the manufacturer not debouncing with an SR latch? Or does the switch really bounce so hard that it bounces between both contacts when pressed? – Richard Hansen Mar 6 '13 at 21:06
• You have just extended the life of my extremely expensive Razer Mamba mouse. Thank you! – Oli May 22 '13 at 10:36
• +1 4 years on. You asked where he lived. I know not, but people in eg Brazil have commented that import duties and similar can increase prices to many times the sale price. – Russell McMahon Jul 9 '16 at 1:27
• Amazing, thank you! I have some additional information about the D2FC-F-7N that may be helpful: pressing on the catch had absolutely no effect, but I managed to open it up by lifting up the very bottom of the case at the button end with a screwdriver. I found that my 10 year old spring was simply too stretchy and replaced it with a donor spring from the right mouse button of another mouse. I had trouble putting the spring back on, but figured out that I needed to attach the middle of the spring onto the tiny ridge at the middle attachment point, then stretch the spring over the button end. – Ivan Kozik Jan 24 '17 at 14:14

OP here. It was time to fix my mouse again, and this time around I didn't have enough unused switches left (last time I used sensor sensitivity buttons as donors) in the mouse to replace the bad ones. This time I solved it by buying the cheapest mouse (~5 bucks) and taking switches from there. No waiting for delivery, the switches are identical except for the color, and very cheap in face of alternatives. Not exactly fixing the old ones, but an even better, frugal solution. And the switches are brand new.

• perhaps add this as an edit/update to your original question? – KyranF Jan 28 '16 at 17:03
• I don't think it would be appropriate to edit the original question as it could partially invalidate existing answers. Or something like that. Some SE sites don't like that so I posted my solution as an answer. Besides it's a solution, not a question. – user1306322 Jan 28 '16 at 17:07
• That is a fair argument! – KyranF Jan 28 '16 at 17:37

You also might use the designated "Electrical Contacts Cleaner", if just spray on the switch. Those avoid the dismantles. Youtube has a video: Logitech MX Revolution mouse repair

• This does work but in the case of a high-use mouse expect to do this once every month or so. Nothing beats taking it apart and physically cleaning the contacts. – Oli May 22 '13 at 10:35

A small capacitor across the switch may do the trick. Say 100nF or so.

• 100nF combined with a 10k$\Omega$ pull-up gives you a 1ms time constant. Worn out switch contacts may bounce for several 10s of ms, so I'd pick a higher value for the cap. – stevenvh Apr 15 '12 at 10:12
• Even seen some switches bounce for >100 ms.. – m.Alin Apr 15 '12 at 11:13
• @m.Alin - Yes, this site even mentions a switch with a 157 ms(!) bounce when opening. – stevenvh Apr 15 '12 at 15:09
• I had a switch that bounced the whole time you held it. That's when I gave up believing I'd ever find a max bounce time. – gbarry Oct 1 '12 at 17:33

I just exchanged the right and left switch and no more problem. The right click doesn't care about double clicks.

• That's a smart makeshift decision. – user1306322 Feb 1 '14 at 0:25
• When the current switch got too bad to fix it again, I swapped it with another switch from an unused button (sensivity +/−) and it works like new again. So cool advice! – user1306322 Jun 25 '14 at 5:40